1. Field of the Invention
The present invention relates in general to a method for manufacturing an organosilicon polymer containing a silalkylenesiloxane, and in particular to a method of manufacturing, with good yield and without accompanying depolymerization, an organosilicon polymer containing a silalkylenesiloxane as the principal chain, and possessing the same functionality at both ends.
2. Background Information
Because, when compared to dimethylpolysiloxane, organosilicon polymers containing a silalkylenesiloxane as expressed by the general formula (--R.sub.2 Si--C.sub.a H.sub.2a --R.sub.2 SiO--) where R is a monovalent hydrocarbon group and a is a positive integer, scission of the molecular chain by ionic material such as acid or alkali is more difficult, their utilization in specialized fields is being studied. Ring-opening polymerization manufacturing methods, which use cyclic silalkylenesiloxanes as the starting material for manufacturing organosilicon polymers containing this silalkylenesiloxane group, are known; see Izvestiya Akademii Nauk SSSR, Seriy a Khimicheskaya, No. 4, 739-744, April, 1971, Japanese Kokai Patent Application Nos. Hei 4 1992!-65428 (also U.S. Pat. No. 5,087,720, issued Feb. 11, 1992, to Kishita et al) and Hei 4 1992!-65429 (also U.S. Pat. No. 5,117,025, issued May 26, 1992, to Takago et al).
However, these manufacturing methods require the use of a cyclic silalkylenesiloxane, such as 2,2,6,6-tetramethyl-1-oxa-2,6-disilacyclohexane and the like, as the starting material, which compounds are difficult to synthesize at high cost. In addition, these methods, as reported in Izvestiya Akademii Nauk SSSR above, have the drawback of not being able to produce a high yield of the objective organosilicon polymer containing the silalkylenesiloxane group because a part of the polysilalkylenesiloxane tends to depolymerize.
Along with these methods, there is a method for obtaining a silethylenesiloxane of low molecular weight and single-ended functionality from 1,1,3,3-tetramethyl-1-vinyldisiloxane and pentamethyldisiloxane separately (see West German Laid-open Patent Application No. 3,144,627); however, a silethylenesiloxane having the same functionality on both ends has not been offered.